Papermaking pulp, i.e. pulp intended for the manufacture of paper or board, is produced by separating the fibres of a cellulosic material, such as wood, by chemical and/or mechanical means. As a common example, kraft pulp is produced by cooking of wood chips according to the sulphate process. Papermaking pulp may also comprise or consist of recycled fibre, i.e. a fibre material which has previously been incorporated in a paper or board product.
Paper or board is employed as a packaging material either in the form of a single ply product or, often, after conversion into a multi ply product, such as a multi ply paperboard or a corrugated fibreboard. It is required that a box formed from such a packaging material protects its content and withstands buckling, fold and/or collapse under the load of other boxes or goods stacked on top of it.
US 2004/0168781 discloses a paper pulp and a method of making paper pulp. The paper pulp includes at least one of cellulose fibre and mechanical pulp fibre, filler, and noil produced from refined cellulose fibre in a range of 0.1 to 15% by weight of the paper pulp. The noil may be produced by refining cellulose fibre to a Schopper-Riegler number greater than 80.
U.S. Pat. No. 8,231,764 discloses a method of preparing a composition for use as a filler in paper or as a paper coating, comprising a step of microfibrillating a fibrous substrate comprising cellulose in the presence of an inorganic particulate material.
There is a desire in the field to improve the properties of paper or board based packaging materials in respect of maintaining the shape of a box formed from such packing materials and/or of maintaining the condition of goods inside the box, e.g. when the box is under load of other boxes or goods stacked on top of it.